HARRIS COUNTY, Texas - After more than a dozen years as a school bus driver for Cypress-Fairbanks ISD, Susan Moore has plenty of stories to tell.

But nothing quite like this -- her bus burst into flames Thursday afternoon on the way home from Cook Middle School.

Related: Cy Fair ISD bus catches fire with students onboard

"I couldn't believe it would go up so fast," she said. "I was ever so glad I got the children out of there."

Moore smelled burning rubber and then noticed smoke coming up through the front dash of the school bus. That's when she got on the public address system and ordered the students to evacuate.

"They calmly and quickly exited the bus," recalled Moore, who added the students take part in regular safety drills. "Half of them went out the front and and the other half went out the back."

Photos: Cy Fair ISD bus catches fire

Once the students were outside, the bus caught fire and the flames quickly engulfed the front part of the vehicle.

Cy-Fair ISD is investigating what caused the fire. The district says the bus was made in 2008 and hasn't had any major maintenance issues. The NTSB will assist in investigating the incident.

Moore , who is a substitute bus driver, is just happy she and the 20 students got out safely.

"I did what I was trained to do," said Moore. "I knew those kids were safe, I knew they went home."